i felt like removing it last time... but after considering it seriously, i decided to leave it there.
Reason for taking out:
better pick up due to lesser mass F=ma
Fuel economy is negligible considering the amount of work done, its really negligible.
Reason for staying inside:
No need call tow truck when puncture tyre
Increase in stability due to lower CG (negligible too)
In case kena kissed hard from behind, there is a spare tyre to protect you (told by dex1999)
So comparing all the pros and cons, its wiser to leave it there....